1. Field of the Invention
The present invention relates to an image forming apparatus having a self-repair function for repairing a fault, when there occurs such a fault that a predetermined function is not sufficiently developed.
2. Description of the Related Art
In the field of an image forming apparatus such as a copying machine, it is proposed that a so-called self-repair function is added. The self-repair function is a function aiming at "functional maintenance" by fault diagnosis of a functional portion related to image formation and repair of a function. The prior art of an apparatus having such a self-repair function is disclosed in U.S. patent application Ser. No. 07/588,191 issued as U.S. Pat. No. 5,166,934), for example, according to the prior application of the present applicant.
In the prior art, an image forming apparatus to be self-repaired is represented as a cause and effect relation among a plurality of physical parameters, a physical parameter to be operated at the time of a fault is searched for on the basis of qualitative inference, and the physical parameter is operated, to repair the fault.
Furthermore, as the other prior art, a functional redundancy type image forming apparatus with a self-repair function is disclosed in U.S. patent application Ser. No. 07/989,512 (issued as U.S. Pat. No. 5,396,314), for example, according to the prior application of the present applicant. Self-repair based on functional redundancy is to develop, when a fault occurs in an apparatus, a function which should have been developed by a certain part which failed by utilizing the potential function of a part which originally existed in the apparatus.
In either self-repair type image forming apparatus according to the prior art, the construction thereof is new and epoch-making in that the fault is self-repaired. However, it is difficult to determine a manipulated variable of a physical parameter at the time of repairing the fault. Specifically, a physical parameter to be operated so as to repair the fault and an alternative part can be satisfactorily raised. However, it is impossible to determine a manipulated variable of a physical parameter, determine a manipulated variable when there are a plurality of alternative parts, and suitably select a part on which little secondary effect is exerted.